Fixes for -G/--globstar (re: 5312a59d)

The fix for '.' and '..' in regular globbing broke '.' and '..' in
globstar. No globstar pattern that contains '.' or '..' as any
pathname component still matched. This commit fixes that.

This commit also makes symlink/** mostly work, which it never has
done in any ksh93 version. It is correct and expected that symlinks
found by patterns are not resolved, but symlinks were not resolved
even when specified as explicit non-pattern pathname components.
For example, /tmp/** breaks if /tmp is a symlink (e.g. on macOS),
which looks like a bug.

src/lib/libast/include/glob.h,
src/lib/libast/misc/glob.c: glob_dir():
- Make symlink/** work. we can check if the string pointed to by
  pat is exactly equal to *. If so, we are doing regular globbing
  for that particular pathname element, and it's okay to resolve
  symlinks. If not (if it's **), we're doing globstar and we should
  not be matching symlinks.
- Let's also introduce proper identification of symlinks (GLOB_SYM)
  and not lump them in with other special files (GLOB_DEV).
- Fix the bug with literal '.' and '..' components in globstar
  patterns. In preceding code, the matchdir pointer gets set to the
  complete glob pattern if we're doing globstar for the current
  pathname element, null if not. The pat pointer gets set to the
  elements of the pattern that are still left to be processed;
  already-done elements are trimmed from it by increasing the
  pointer. So, to do the right thing, we need to make sure that '.'
  or '..' is skipped if, and only if, it is the final element in
  the pattern (i.e., if pat does not contain a slash) and is not
  specified literally as '.' or '..', i.e., only if '.' or '..' was
  actually resolved from a glob pattern. After this change,
  '**/.*', '**/../.*', etc. do the right thing, showing all your
  hidden files and directories without undesirable '.' and '..'
  results; '.' and '..' are skipped as final elements, unless you
  literally specify '**/.', '**/..', '**/foo/bar/..', etc.

src/cmd/ksh93/COMPATIBILITY:
- Note the symlink/** globstar change.

src/cmd/ksh93/sh.1:
- Try to document the current globstar behaviour more exhausively.

src/cmd/ksh93/tests/glob.sh:
- Add tests. Try to cover all the corner cases.

src/cmd/ksh93/tests/shtests:
- Since tests in glob.sh do not use err_exit, they were not
  counted. Special-case glob.sh for counting the tests: count the
  lines starting with a test_* function call.

Resolves: https://github.com/ksh93/ksh/issues/146

NEWS

@@ -3,6 +3,16 @@ For full details, see the git log at: https://github.com/ksh93/ksh
 
 Any uppercase BUG_* names are modernish shell bug IDs.
 
+2021-03-07:
+
+- Fixed a bug with -G/--globstar introduced on 2020-08-09: patterns did not
+  match anything if any pathname component was '.' or '..', e.g. '**/./glob.c'
+  never matched. The 2020-08-09 fix does still apply to patterns like '.*'.
+
+- Enhancement to -G/--globstar: symbolic links to directories are now followed
+  if they match a normal (non-**) glob pattern. For example, if '/lnk' is a
+  symlink to a directory, '/lnk/**' and '/l?k/**' now work as you would expect.
+
 2021-03-06:
 
 - Fixed an old expansion bug: expansions of type ${var=value} and ${var:=value}